AN fittings get a 37-degree flare. When you slam on the brakes, your master cylinder is applying on the order of 1,800 psi to the lines, fittings, calipers, and wheel cylinders.

1. Most brake line kits are available in either mild or stainless steel line and with the option of traditional 45-degree double or 37-degree AN flare fittings.

This type of brake line flaring tool will work if your material is soft, you get a good cut, and presumably have to hold your tongue just so.

Brake line wrenches (flare nut wrenches or simply line wrenches) serve a specific purpose. Domestic cars often use 7/16-inch and imports 10 mm.

Flaring metal brake lines and metal fuel lines (or transmission lines) is something of an art when using the most common type of double flaring tool. We're talking about the mass-produced double ...